I would say neither. Nitto usually uses a hard compound of tire. I've had the 555's and 450, and both sucked, especially in cold mornings. With the harder compound you'll experience a rougher feeling ride, making bumps more noticeable.
I tried out the Dunlop FM901's, since I've had the SP9000's before. I like both, and can't complain any which way about the 901's except that with them being softer, they also wear out faster.
I've had Bridgestones before as well, many different types, and love any set of tires they make, never had problems. Compound is roughly the same as the Dunlops, but a bit better.
Yokohamas are OK, but I have experienced excessive noise and they wear out really quick, having had the A520's and Paradas. Ride is comfortable though.